Transcript for Las Vegas country music festival underway, as shooter prepares in hotel: Part 2
Reporter: A casino employee told me 2010 Saturday night and Sunday morning she watched paddock play the high stake section of the casino for hours and hours on end. He was there until 7:30, at least, in the morning of the day of the shooting playing that video poker. If gambling is one of his demon he wanted to get one more fix, and maybe also it pumped up his anger and rage. We just got up and had breakfast, and wanted to watch some football. And then just kinda hung out until we decided to go over to the venue. We just were hanging out at the house and, just putting on outfits and stuff and just so excited for the festival. We flew into Vegas, went straight to the festival. Checked in. We started walking into the festival and I took a quick Snapchat and the caption read wonder what kind of trouble can I get into tonight. My parents didn't really like us going places without them, and they were like oh, your seniors and you're almost 18 so they were just like, we'll just let you guys go without us this time. We -- stay at the luxor every year. It's right across the street from the venue. It's right next to the mandalay bay. Sunday, I'd gotten the call -- "Hey, do you want to work tonight?" "Yeah, sure, I'll be there." On Sunday there was app whole series of entertainment options. David copperfield, a show called Michael Jackson's one playing at the manned day bay in addition to the route 19 harvest festival. Las Vegas was alive and jumping as it is every night. We went on stage and there were a lot of people at the festival. It takes about 15 minutes. Went to the venue and I got dropped off right out front. Just the excitement and energy were off the charts and everybody is in there, you know, amazing, cowboy gear and looking so cute. We'll see what you got las Vegas. Over the weekend as down below people are drinking beer and reveling in this route 91 harvest festival, paddock sent up the command center and he is slowly stockpiling this massive arsenal in his room. He's got 10 cases, there are 24 guns, and included among them are at least a dozen ar rifles, those are long guns. One thing we have never seen in the history of lone shooters is the elaborate system he has enveloped himself in inside the room. He's got a baby monitor set up. Cameras, one hidden under a plate. He had installed the camera right in the peep hole of his door. The purpose is that he would be able to monitor from inside the room if law enforcement approaches. He's ordering room service and those trays are coming in but notably he didn't want house keeping in there messing with his stuff. He had that do not disstate your name sign out on the door. That day was amazing and a lot of people and different bands playing. ??? C'mon ??? ??? whoa ??? So, I want to say I got there close to 9:30, was when my shift was about to start, when the talent leaves the stage, we get up there. And we start tearin' it all out. The venue was set up incredible. You just felt like you were safe, because we went through metal detecters. They looked in our purses. I think, with the training and the background that I have, I'm always lookin' for exits, no matter what. I do remember -- looking at those fences and lookin', like, "How do we get out, if something goes wrong?" There were so many people like, everyone was really nice to each other, even random people, they would come up and dance with you. It was really fun. We're all excited, happy, and the music is incredible. Music always touches our hearts and lives. Us girls we like those cowboys that sing the cowboy songs that bring about love and fun and happiness. Make this place shake tonight. I just remember, it was just such a great vibe at that point. ??? So I got friends ??? All of a sudden journey came on. And you hear this entire crowd just start singing. ??? We were dancing to -- as much as you could, shoulder to shoulder. ??? it was -- it kinda was, like a throwback to the '60s of, you know, peace, love and happiness. Every year we go we stand in the same place next to the vip booth and this particular day we went to the other side. The other side of the stage. ??? and ah, that was a game changer for us. One of the most moving parts of the whole three days was they sang "God bless America." The whole crowd was singing at the top of their lungs and had their phones lit up. ??? Reporter: As the music is playing there's a different sound happening on the 30th floor. He's using a hammer to smash through at least two win ghoes the suite to gain a vantage point down below. I was looking forward to Jason aldean. Jason aldean is huge. ??? The whole vibe of the show is upbeat and fun and loud. Jason aldean started. I was so excited to see him. ??? You have the sickening feeling that none of these people down below had any idea of the carnage that was just about to befall them. We had the vip wrist bands for the neon tent. We took a photo, her and I took a photo. After that photo, the contrast was so dramatic. It was the calm before the storm. You had not a care in the world. Two minutes later, literally two minutes later, I looked at the time stamp and everything changed.
This transcript has been automatically generated and may not be 100% accurate.